fn distance(tile: u8, index: usize) -> u32 {
    let target: usize = (tile - 1) as usize
    let row: usize = index / 4
    let col: usize = index % 4
    let targetRow: usize = target / 4
    let targetCol: usize = target % 4
    let dr: u32 = ifLess(row, targetRow)
    let dc: u32 = ifLess(col, targetCol)
    return dr + dc
}

fn ifLess(a: usize, b: usize) -> u32 {
    if a < b {
        return (b - a) as u32
    }
    return (a - b) as u32
}

pub fn main(world: World) -> Void raises {
    if distance(5, 0) == 1 {
        check world.out.write("15 puzzle solver ok\n")
    }
}